This invention relates to a liquid filter, in particular an oil filter, for cleaning lubricant oil, in particular for internal combustion engines in motor vehicles.
International Patent WO 99/39 802 describes a liquid filter which has a ring filter insert accommodated in a filter housing made of plastic, a feeder channel carrying crude liquid and a return channel which carries away the clean liquid. The feeder channel and the return channel are arranged in a collecting space of the filter housing, and this collecting space is bordered by a safety wall designed in one piece with the filter housing extending radially around the feeder channel and the return channel. The filter housing must be mounted securely on a component which has a feeder line for unpurified oil and an outlet for purified oil. The filter housing is usually mounted on the engine block of the engine. However, in the case of a sealed mounting of a filter housing made of plastic on this component, problems may arise because relatively high pressures prevail in the feed and in the outlet. Because of special installation conditions, it may occasionally be necessary to seal the filter housing with respect to the engine block by means of gaskets which act axially. In the case of a filter housing made of plastic, there is then the disadvantage that the contact forces required, with which the filter housing is clamped against the engine block, cannot be introduced into the plastic housing.
German Patent 39 03 675 C2 describes an oil filter whose filter housing contains a filter receiving space in an upper section to accommodate a ring filter insert and in a lower section it has a feeder channel for unpurified oil and an outlet channel for purified oil. The filter housing having the channels integrated into it is usually made of metal as a one-piece injection-molded component. In this way the required prestressing forces and contact pressure forces can be introduced into the metal housing to achieve a sufficient sealing effect with gaskets that act axially. However, in order to form smooth surfaces for gaskets, e.g., for the internal channels in the interior of the injection-molded housing produced in this way, immediate remachining of the injection-molded component is necessary. In machining the metal housing, cavities may be encountered due to porosity and shrink holes, necessitating a complicated remachining of the component.
The present invention is concerned with the problem of providing a design for a liquid filter of the type defined in the preamble that will allow the use of gaskets that act axially and can also be manufactured relatively inexpensively.
This problem is solved according to this invention by a filter having the features of claim 1.
This invention is based on the general idea that at least one part of the components of the filter housing, which are manufactured in one piece with the filter housing in the case of a traditional filter housing and must be remachined to fulfill their function, is combined in a function carrier insert that can be manufactured separately, and the axial seal with respect to the component on which the filter housing is to be mounted tightly is implemented by a screw connection of the filter housing onto the component. This yields on the one hand the possibility of an external remachining of these function elements, while on the other hand the function carrier insert may also be manufactured in such a way that remachining may be omitted. For example, the function carrier insert is made of plastic, in particular by an injection molding process. The surface quality produced in this way is of a sufficiently high grade so that remachining can usually be omitted. In addition, the filter housing made of metal has sufficient strength to produce a sufficient axial clamping effect, which in turn produces a sufficient axial pressing force for the axial gaskets. On the whole, this yields a liquid filter that can be manufactured especially economically.
Other important features and advantages of the device according to this invention are derived from the subclaims, the drawings and the respective description of the figures on the basis of the drawings.
It is self-evident that the features mentioned above and those to be explained below can be used not only in the respective combination indicated but also in other combinations, or they may be used alone without going beyond the scope of the present invention.